EDAC, skx: Fix skx_edac build error when ACPI_NFIT=m

Prevent build error when CONFIG_ACPI_NFIT=m and CONFIG_EDAC_SKX=y by
limiting EDAC_SKX based on how ACPI_NFIT is set.

Fixes this build error:
  drivers/edac/skx_edac.o: In function `get_nvdimm_info':
  ../drivers/edac/skx_edac.c:399: undefined reference to `nfit_get_smbios_id'

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Fixes: 58ca9ac1463d ("EDAC, skx_edac: Detect non-volatile DIMMs")
Link: http://lkml.kernel.org/r/3af91354-8e19-d2af-1bba-ced8dce053f1@infradead.org
Signed-off-by: Borislav Petkov <bp@suse.de>

drivers/edac/Kconfig

@@ -232,6 +232,7 @@ config EDAC_SBRIDGE
 config EDAC_SKX
 	tristate "Intel Skylake server Integrated MC"
 	depends on PCI && X86_64 && X86_MCE_INTEL && PCI_MMCONFIG
+	depends on ACPI_NFIT || !ACPI_NFIT # if ACPI_NFIT=m, EDAC_SKX can't be y
 	select DMI
 	help
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